蜡蚧刺束梗孢(Akanthomyces lecanii)的线粒体基因组特征与系统发育分析

Sequence characteristics and phylogenetic relationship of the mitochondrial genome of Akanthomyces lecanii

摘要:

【背景】蜡蚧刺束梗孢(Akanthomyces lecanii)是重要的生防类虫生真菌，其线粒体基因组详细信息未见报道。【目的】系统研究蜡蚧刺束梗孢线粒体基因组信息，有助于明确该菌准确的系统发育地位，并为虫草科(Cordycipitaceae)真菌物种的系统发育、资源保护和开发利用提供分子依据。【方法】通过对蜡蚧刺束梗孢RCEF6920完整线粒体基因组进行测序，利用生物信息学分析其组成特征、序列重复、系统发育分析、共线性分析，以及与其他虫草科真菌线粒体基因组进行比较。【结果】菌株RCEF6920的环状线粒体基因组全长24 577 bp，共编码43个基因，由15个蛋白质编码基因、2个rRNA基因和26个tRNA基因组成。仅鉴定出一个内含子，其阻断rnl基因并鉴定出编码核糖体蛋白S3 (rps3)的开放阅读框(open reading frame, ORF) orf447。基因组核苷酸组成存在A+T偏移(72.89%)。26个tRNA基因可转运全部20种氨基酸，并表现为典型的三叶草结构。蛋白质编码基因中频率最高的密码子是AGA，其中精氨酸和亮氨酸出现频率最高，蛋氨酸和色氨酸出现频率最低。蛋白编码基因的系统发育关系显示，刺束梗孢属(Akanthomyces)和萨姆森虫草属(Samsoniella)互为姊妹属。与虫草科其他物种相比，蜡蚧刺束梗孢线粒体基因组较小，除部分虫草属(Cordyceps)物种外，在虫草科物种共线性较好。【结论】本研究获得了蜡蚧刺束梗孢的线粒体基因组全序列及相关信息。蛋白编码基因的系统发育分析支持了蜡蚧刺束梗孢的独立分类地位，也表明虫草科真菌线粒体基因组结构较保守。

关键词:蜡蚧刺束梗孢;线粒体基因组;虫草科;比较分析;系统发育分析

Abstract:

[Background] Akanthomyces lecanii is an important entomogenous fungus for biocontrol, and its mitochondrial genome has not been reported. [Objective] The mitochondrial genome of A. lecanii was systematically studied, which would help clarify the taxonomic status of this fungus and provide a molecular basis for the phylogenetic research and the resource protection and utilization of Cordycipitaceae. [Methods] The full-length mitochondrial genome of A.lecanii RCEF6920 was sequenced, and bioinformatics tools were used to probe into the composition, sequence repeats, phylogenetic relationship, and collinearity. Furthermore, the mitochondrial genome was compared between A.lecanii and other species of Cordycipitaceae. [Results] The mitochondrial genome of A.lecanii RCEF6920 was a circular DNA molecule of 24 577 bp and contained 43 genes, including 15 protein-coding genes, 2 rRNA genes, and 26 tRNA genes. Only one intron was detected in the mitochondrial genome, and it interrupted rnl and contained orf447 encoding ribosomal protein S3. The nucleotide composition of the mitochondrial genome was A+T biased (72.89%). The 26 tRNA genes could transfer all the 20 amino acids and presented a typical cloverleaf structure. AGA was the most frequently used codon of the protein-coding genes. Arginine and leucine were identified as the most common amino acids, while methionine and tryptophan were the least common amino acids in the protein-coding genes. The phylogenetic analysis based on the protein-coding genes revealed that Akanthomyces and Samsoniella were sister genera. Compared with other species of Cordycipitaceae, A.lecanii had a small mitochondrial genome. Except several species, other species of Cordycipitaceae had good mitochondrial genome collinearity. [Conclusion] We obtained the full-length mitochondrial genome sequence and related information of A.lecanii. The phylogenetic analysis supports the independent taxonomic status of A. lecanii, and the mitochondrial genomes of fungi belonging to Cordycipitaceae are conserved.

Key words:Akanthomyces lecanii;mitochondrial genome;Cordycipitaceae;comparative analysis;phylogenetic analysis